1. Field of the Invention
This invention relates to the field of marine vessels. More specifically, the invention comprises a wind-powered vessel having a gimbaled mast and winged keel.
2. Description of the Related Art
Sail-powered surfboards, canoes, and similar watercraft have come into widespread use during recent years. Most of these devices employ a fairly rigid mast attached to a surfboard by a pivot joint. Some, however, employ a large xe2x80x9ckitexe2x80x9d-type sail in place of a fixed one. This kite type sail is attached to the end of a long tether and may be allowed to ascend many feet ahead of and above the vessel. FIG. 1 shows one example of such a sail, designated as sail 10. FIG. 1 does not show a prior art device. In a prior art device, main sheet 14 would typically be attached to a harness worn by a person riding atop hull 18. It would not be attached directly to the craft.
Those skilled in the art will know that sail 10 can be adjusted in elevation such that the angle between main sheet 14 and the vessel approaches and exceeds forty-five degrees. In such a case, main sheet 14 (whichxe2x80x94being a ropexe2x80x94only transmits tensile force) can exert considerable lifting force on the vessel. The vessel is only maintained on the surface via the weight of itself and its rider.
Those skilled in the art will also know that sail 10 will be blown in the direction of wind travel. The rider may not wish to go in this direction. However, when attempting to steer the prior art xe2x80x9ckitexe2x80x9d-powered vessels off this course, the vessel tends to xe2x80x9cskidxe2x80x9d along the surface rather than maintaining the desired course. The experienced rider must xe2x80x9ccut an edgexe2x80x9d of the board into the water to provide a source of lateral resistance.
The present invention comprises a modified mast and keel system for a sailing vessel. The mast is gimbaled to the hull, so that it can move in pitch and roll. A downward extension of the mast pivotally connects to a winged keel. An aft strut also pivotally connects to the hull and pivotally connects to the winged keel. The hull, the mast extension, the winged keel, and the aft strut combine to form a traditional four bar linkage which can be used to adjust the angle of attack of the winged keel with respect to the vessel. The four bar linkage can be set so that the winged keel maintain a constant pitch with respect to the hull. It can also be set to vary the pitch of the winged keel as the mast pivots upward and downward. Thus, the amount of downward or upward force created by the winged keel can be varied.
As the mast rolls in one direction, the winged keel rolls in the same direction beneath the hull, in order to keep the downforce generated by the winged keel in axial alignment with the forces placed on the hull by the gimbaled mast. As the mast pitches in one direction, the winged keel pitches in the same direction, again to keep the downforce in axial alignment with the mast.